Product Version: NetBeans IDE Dev (Build 200708270000)
Java: 1.6.0_02; Java HotSpot(TM) Client VM 1.6.0_02-b05
System: Windows XP version 5.1 running on x86; Cp1251; ru_RU (nb)
Steps to reproduce:
Open any heapdump file. (I use an Netbeans heapdump and it has about 290000 instances of String).
Select java.lang.String class in classes view and open it in Instances view.
Select first instance in Instances pane using mouse.
- Update of Fields and References panes takes about 2 seconds.
Scroll through instances with keyboard (for example from 1 to 30 instance).
- Update of Fields and References panes takes more than a minute.

I would say this is not scrolling but sequential selecting. There is an easy workaround for scrolling - use the
scrollbar. When explicitly selecting an instance, I would expect that you want to see the details for it.
Anyway, a fix will be implemented that cancels resolving fields/references when another instance is selected. Not for 6.0.